Response of the Solar Five-Minute Oscillations to a Major Flare

Abstract

Solar five-minute oscillations of intermediate-degree ℓ were observed both before and after a very strong white-light flare. Intensity images of the full Sun taken on two sides of the Fe I λ 5576 spectral line were recorded on film, digitized with 8" spatial resolution, and then converted into Doppler velocities. The data were projected onto both equatorial and polar sectoral modes and Fourier transformed in time. Comparing the resulting power spectra, we find a substantial increase in power in the ps ridge of the equatorial modes on the day after the flare; such an increase may be a consequence of the solar flare. When data from all the ridges are considered, there is an average increase in power of only a few percent the day after the flare. This overall increase is probably not significant due to uncertainties from effects of the beating of unresolved modes.